it's not that he didn't try to rip apart romney's economic plan. >> that kind of top-down economics, where folks at the top are doing well, so the average person making 3 million bucks is getting a $250,000 tax break, while middle class families are burdened further. >> reporter: romney was determined to go toe to toe. >> but virtually everything he just said about my tax plan is inaccurate. >> all right. go ahead. >> so if the tax plan he described were a tax plan i was asked to support, i would say, absolutely not. >> reporter: the president did get digs in. >> for 18 months, he's been running on this tax plan. and now, five weeks before the election, he's saying that his big, bold idea is, never mind. >> reporter: but he also showed flashes of the kind of testiness sources in both camps feared from their candidates, except obama's was directed a the moderator, not romney. >> the last point i'd make, before -- >> two minutes is up, sir. >> no, i think i had five seconds before you interrupted me, was -- >> reporter: romney did have his own awkward moderator moment. >> i'm sorry, ji